The design is done in KiCAD, which is Open Source electronics design program. We’ll
clear up the schematics and publish full parts list with distributors so you can
even assemble your own boards if you want to! All this is still quite a lot of work,
so please give us a few weeks to polish the design as we publish it.

We’ll work to merge the PCB footprints created for the board back to KiCAD upstream
during the campaign, your backing allows us to expand the common Open framework for
electronics design.

We would like to thank the community and awesome support we have had ever since the
beginning. Especially Vaasa’s Hackerspace’s contribution to us was extremely
important, as they found out about the transient vulnerability in Ethernet PHY of
Raspberry Pi. Open developing of the boards with the community let us find a
critical design flaw, which is now fixed before our release. Even if our campaign is
not successful, the knowledge we gained during this spring is now out in the open
where everyone can benefit from it.

There has been a lot of interest in building derivative works based on our board. As
we’re committed to values of Open Source, we’re always happy to see our designs grow
into something else. Please contact us with your ideas and suggestions, even if it’s
just to let us know that you’re making something cool. This way we can focus at
something else at ELL-i and avoid duplicating work.

We setup the Helsinki Hacklab for our hackathon. It was a quick matter of connecting our PoE switch to rack and presenting the Raspberrys and PoE shields, PoELL-i Nucleos and various electronics modules, parts and shields. Soon we were having music over Ethernet.

It was very interesting to see what happens when the area has a lot of creative people, and facilities to support them around. Helsinki Hacklab had Ethernet sockets already available all over the place, and with our PoE switch we could enable PoE in any socket in less than a minute.

Whenever there was a convenient spot for building a project, things happened at amazing pace. Want to try if that stepper motor driver can drive the curtains, but don’t want to risk your laptop to higher-than-USB-voltages? Plug in a Raspberry with PoE, power Arduino through Raspberry Pi’s USB and you’re ready to go!

There was something amazing created in our hackathon, and we feel it deserves it’s own in-depth writeup. Stay tuned to find out what it was! In meanwhile, join in our mailing list here and we’ll email you before our campaign starts so you can snatch those Early Bird rewards!

We tested the boards, full 100MBit/s speed was reached. The next test was to see if our clamping diodes work as they should, so it was oscilloscope o’clock.

Before protection diodes

After protection diode

The protection diode clamps the voltage spike to roughly 9 volts. Next thing to do was to plug the cable in and out ~100 times and see if the board would still connect. And connect it does! Now all that remains is to do a few cosmetic adjustments and launch the campaign.

As the board is getting ready for a launch, there is one big question remaining: How to name it? We cannot call it HAT, since our board doesn’t have ID EEPROM and it’s longer than the official specification. Most of us in ELL-i are engineering types and terrible at naming things, so we’re turning to You for help. Send your suggestions for the name of board to indie@ell-i.org by Friday 22.5, we’ll vote on the name in our upcoming Hackathon. There is a prize for winner: we’ll assemble one of the prototype boards by hand and send it to you anywhere in world where the Finnish mailman dares to go.

Also be sure to sign up in our mailing list here and we’ll send you a mail before the campaign launches so you can grab those early bird special deals.

Our newest boards are currently in customs waiting to be cleared, they will arrive in time for our Hackathon next weekend.

We took this opportunity to make a few final adjustments to design. We added a connection for a pin header at the output before fuse in case someone wants to power some external load. To further help with external loads we also left a place for output voltage adjustment resistors so people can tweak the output to suit their needs.

We also pulled the DC/DC module a bit inwards to the board so it will have a bit more space between HiFiBerry DAC+ RCA-connector and DC/DC transformer.

We’re going to launch the crowdfunding campaign soon. In meanwhile, if you want to receive one board ASAP we can send you the bare boards and parts at no markup. If you’re interested in assembling one board and giving it a try, contact us at indie@ell-i.org and we’ll arrange things from there.

Last week we discovered that our PoE for Raspberry Pi eventually breaks the Ethernet port of connected Raspberry Pi. Since we have a few units which have been running constantly for almost two weeks, we started to suspect that the problem is in connection/disconnection transients. The first step was to find out if these connection/disconnections really were the cause of the problem, so we powered a Raspberry Pi separately and plugged the Ethernet connection a few tens of times. The Ethernet port of Pi stopped working quickly, and we had the isolated the cause of failure.

Time for some oscilloscope shots: the oscilloscope was connected on a differential pair after the transformer. Red and blue are differential wires, pink is the voltage differential between the two.

This was one of the cleaner events on the cable, with only one clear spike on it. Our initial suspicions are confirmed, the ~57V on the unloaded PoE line gets coupled to the data lines. The recommended protection against these electrical transients is to add clamping diodes across the transformer pins. We had some suitable zener diodes lying around, so it was a quick matter of connecting them in antiseries and soldering them down on pins of the transformer.

Time to take an another look with the oscilloscope. This time I caught a real monster of a cable transient on a tape:

Even while the supply lines bounce around relative to ground, they stay nicely within 3 V swing relative to one another. This means that the attached Raspberry Pi should receive a lot less electrical stress from these events.

The attached Pi did survive a long series of cable connections, but it still could not form a link with the switch. On a hunch I forced the data rate down to 10 Mbit/s, and the Raspberry Pi was happy to communicate at that rate.

The degradation of speed down to 10Mbit/s is not acceptable, but hopefully this will not be a problem when we use lower-capacitance surface mount diodes close to transformer pins. There always is a option of using specialty ultra-fast, low capacitance transient voltage suppressor arrays if zeners seem to cause problems.